1. Field of the Invention
The present invention relates generally to radio frequency identification (RFID) systems, and more particularly, to a method and system for automatic adjustment and diagnosis of RFID systems using programmable checktags.
2. Description of Related Art
In the automatic data identification industry, the use of radio frequency (RF) transponders (also known as RF tags) has grown in prominence as a way to track data regarding an object on which an RF transponder is affixed. An RF transponder generally includes a semiconductor memory in which information may be stored. An RF interrogator containing a transmitter-receiver unit is used to query an RF transponder that may be at a distance from the interrogator. The RF transponder detects the interrogating signal and transmits a response signal containing encoded data back to the interrogator. RFID systems are used in applications such as inventory management, security access, personnel identification, factory automation, automotive toll debiting, and vehicle identification, to name just a few.
Such RFID systems provide certain advantages over conventional optical indicia recognition systems (e.g., bar code symbols). For example, the RF transponders may have a memory capacity of several kilobytes or more, which is substantially greater than the maximum amount of data that may be contained in a bar code symbol. The RF transponder memory may be re-written with new or additional data, which would not be possible with a printed bar code symbol. Moreover, RF transponders may be readable at a distance without requiring a direct line-of-sight view by the interrogator, unlike bar code symbols that must be within a direct line-of-sight and which may be entirely unreadable if the symbol is obscured or damaged. An additional advantage of RFID systems is that several RF transponders may be read by the interrogator at one time.
RF tags may either be xe2x80x9cactive,xe2x80x9d containing their own RF transmitter, or xe2x80x9cpassive,xe2x80x9d having no transmitter. Passive tags, i.e., tags that rely upon modulated back-scattering to provide a return link to an interrogating base station, may include their own power sources, such as batteries, or they may be xe2x80x9cfield-powered,xe2x80x9d whereby they obtain their operating power by rectifying an interrogating RF signal. Although both battery-powered and field powered tags have minimum RF field strength read requirements, or read thresholds, in general, a field-powered passive system requires at least an order of magnitude more power in the interrogating signal than a system that employs tags having their own power sources. Because the interrogating signal must provide power to a field-powered passive tag, the read threshold for a field-powered passive tag is typically substantially higher than for an active tag. However, because field-powered tags do not include their own power source, they may be substantially less expensive than active tags; and because they have no battery to xe2x80x9crun down,xe2x80x9d field-powered passive tags may be more reliable in the long term than active tags. And, because they do not include a battery, field-powered passive tags are typically much more xe2x80x9cenvironmentally-friendly.xe2x80x9d
One of the primary disadvantages of prior art RFID systems is that their initial installation and ongoing maintenance has been a highly manual operation. For example, a typical installation of a RFID system requires a field engineer to travel to the installation location and identify the read zone for the particular installation. Once the read zone has been identified, a checktag is placed in the read zone and the interrogator is manually adjusted (e.g., using a screwdriver) to provide the desired RF power and noise injection settings. In many applications, the checktag is physically wired to the interrogator. Once the initial installation of the RFID system is complete, ongoing maintenance may be required as various operational and environmental conditions affect the performance of the system. This ongoing maintenance has similarly been a highly manual operation, requiring the field engineer to return to the system location and make the necessary required adjustments. In some applications, the checktags have included some capability for remote diagnostics; however, the capability has been limited to a simple go/no-go analysis without the ability to remotely adjust the operating parameters of the interrogator. As a result, it has not yet been possible to automate the ongoing maintenance of these RFID systems.
Accordingly, it would be very desirable to provide a method and system for automatically and remotely adjusting and diagnosing RFID systems using programmable checktags.
The present invention provides a method and system for automatically and remotely adjusting and diagnosing RFID systems using programmable checktags. More particularly, the present method and system automatically adjusts RFID transmission parameters in order to read RFID tags within a spatially defined read zone while excluding RFID tags in a no-read zone.
In an embodiment of an automatic RFID adjustment system of the present invention comprises a controller adapted to send and receive data from a plurality of transponders, organized into a first and second subset of transponders. The controller may further comprise computer software adapted to run a power adjustment program, a radio including a transmitter and receiver, and a digital signal processor adapted to adjust the transmission parameters of the system. The first subset of the plurality of transponders is located in a spatially defined read zone, and the second subset of transponders is located in a spatially defined no-read zone. When the automatic adjustment program is selected, the RFID adjustment system automatically queries the first and second subsets of transponders, and adjusts transmission parameters to read all transponders in the read zone but to exclude the transponders in the no-read zone.
The present invention further comprises a method of automatically adjusting the radio frequency transmission parameters between the controller and the selected plurality of transponders. Initially, the controller transmits a signal to the first subset of transponders located within the read zone, and analyzes any responsive signals from the first subset of transponders. The controller adjusts transmission parameters to ensure that all transponders within the read zone receive signals from and return signals to the controller. The controller next transmits a signal to the second subset of transponder located in the no-read zone, and analyzes any responsive signals from the second subset of transponders. The controller then adjusts transmission parameters to ensure that all transponders located in the no-read zone do not respond to query transmissions by the controller. These steps are re-performed in a loop type operation until all transponders in the read zone are queried, and all transponders in the no-read zone are not queried.